 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.actions;

 import org.eclipse.jface.action.Action;
 import org.eclipse.ui.IPartListener;
 import org.eclipse.ui.IWorkbenchPart;

 /**
  * The abstract superclass for actions that listen to part activation and
  * open/close events. This implementation tracks the active part (see
  * <code>getActivePart</code>) and provides a convenient place to monitor
  * part lifecycle events that could affect the availability of the action.
  * <p>
  * Subclasses must implement the following <code>IAction</code> method:
  * <ul>
  * <li><code>run</code> - to do the action's work</li>
  * </ul>
  * </p>
  * <p>
  * Subclasses may extend any of the <code>IPartListener</code> methods if the
  * action availablity needs to be recalculated:
  * <ul>
  * <li><code>partActivated</code></li>
  * <li><code>partDeactivated</code></li>
  * <li><code>partOpened</code></li>
  * <li><code>partClosed</code></li>
  * <li><code>partBroughtToTop</code></li>
  * </ul>
  * </p>
  * <p>
  * Although this method implements the <code>IPartListener</code> interface,
  * it does NOT register itself.
  * </p>
  */
 public abstract class PartEventAction extends Action implements IPartListener {

     /**
      * The active part, or <code>null</code> if none.
      */
     private IWorkbenchPart activePart;

     /**
      * Creates a new action with the given text.
      *
      * @param text the action's text, or <code>null</code> if there is no text
      */
     protected PartEventAction(String text) {
         super(text);
     }

     /**
      * Creates a new action with the given text and style.
      *
      * @param text the action's text, or <code>null</code> if there is no text
      * @param style one of <code>AS_PUSH_BUTTON</code>, <code>AS_CHECK_BOX</code>,
      * <code>AS_DROP_DOWN_MENU</code>, <code>AS_RADIO_BUTTON</code>, and
      * <code>AS_UNSPECIFIED</code>
      * @since 3.0
      */
     protected PartEventAction(String text, int style) {
         super(text, style);
     }

     /**
      * Returns the currently active part in the workbench.
      *
      * @return currently active part in the workbench, or <code>null</code> if none
      */
     public IWorkbenchPart getActivePart() {
         return activePart;
     }

     /**
      * The <code>PartEventAction</code> implementation of this
      * <code>IPartListener</code> method records that the given part is active.
      * Subclasses may extend this method if action availability has to be
      * recalculated.
      */
     public void partActivated(IWorkbenchPart part) {
         activePart = part;
     }

     /**
      * The <code>PartEventAction</code> implementation of this
      * <code>IPartListener</code> method does nothing. Subclasses should extend
      * this method if action availability has to be recalculated.
      */
     public void partBroughtToTop(IWorkbenchPart part) {
         // do nothing
 }

     /**
      * The <code>PartEventAction</code> implementation of this
      * <code>IPartListener</code> method clears the active part if it just closed.
      * Subclasses may extend this method if action availability has to be
      * recalculated.
      */
     public void partClosed(IWorkbenchPart part) {
         if (part == activePart) {
             activePart = null;
         }
     }

     /**
      * The <code>PartEventAction</code> implementation of this
      * <code>IPartListener</code> method records that there is no active part.
      * Subclasses may extend this method if action availability has to be
      * recalculated.
      */
     public void partDeactivated(IWorkbenchPart part) {
         activePart = null;
     }

     /**
      * The <code>PartEventAction</code> implementation of this
      * <code>IPartListener</code> method does nothing. Subclasses should extend
      * this method if action availability has to be recalculated.
      */
     public void partOpened(IWorkbenchPart part) {
         // do nothing
 }
 }

